If you have a kitchen sink leaking from the plug hole or drain area, here's what's likely causing it and what to do first:
Most common causes:
What to do right now:
Most drain leaks are fixable in under 30 minutes with basic tools.
That said, drain leaks can be sneaky. What looks like a minor drip can quietly soak through cabinet wood, create mold within 24 to 48 hours, and cause hundreds of dollars in damage before you notice anything wrong. A single drip per second wastes around 3,000 gallons of water per year — and hidden water damage in U.S. homes averages $3,000 to $5,000 in repairs.
I'm Jon Miller, Master Plumber and co-owner of JTM Plumbing & Drain in Gretna, Nebraska, and I've been fixing kitchen sink leaking problems since 1993. In this guide, I'll walk you through exactly how to find the source of a drain leak and fix it yourself — and I'll tell you when it's time to call a pro.
When homeowners in Gretna, NE and nearby Nebraska communities ask us, "Why is my kitchen sink leaking underneath?" the answer usually comes down to one of two categories:
If the leak shows up only when water is running or draining, the problem is usually in the drain system. If it drips even when no one is using the sink, check the supply lines or shutoff valves first.
Common warning signs include:
Leaks often start small. Then they quietly damage cabinets, stored items, and sometimes even flooring. If you want a broader look at household leak points, our guide on common types of leaks for your home is a helpful place to start. It is also worth remembering that some under-sink problems stay hidden for a long time, which is why articles like Why Your Kitchen Sink Might Be Leaking Without You Knowing have become so popular.
If the leak is coming from the plug hole area, these are the usual suspects:
The basket strainer is one of the most common failure points. Water sits around that opening every day, and over time the seal can dry out, crack, or shrink. When that happens, water slips past the flange and drips into the cabinet below.
Another common issue is the P-trap. This curved section of pipe holds water to block sewer gases, but it also catches grease and debris. A clog can stress the joints, and old metal traps can corrode until they start dripping. If you have a double-basin sink, the continuous waste tee and tailpieces also add more joints where leaks can develop.
One important DIY tip: on most sink drains, the threads themselves do not make the water seal. The washers and gaskets do. That means wrapping tape around a drain slip joint usually does not solve the real problem. A proper repair usually means tightening the joint correctly or replacing the washer, gasket, or drain assembly. For another walkthrough of drain-side repairs, see How To Fix Kitchen Sink Leak: Fixing Drains From Underneath.
If your sink has a garbage disposal, the leak could be coming from the disposal instead of the drain basket.
Check these spots:
Garbage disposals vibrate every time they run. Over time, that vibration can loosen fasteners and stress gaskets. Sometimes a disposal only leaks when the sink is drained quickly, when both bowls are emptied at once, or when the dishwasher drains. That can make the source easy to miss.
If water appears near the reset button area or along the body of the disposal, the housing itself may be cracked. At that point, replacement is usually smarter than repair. For more on typical disposal and drain leak points, Common Kitchen Sink Leak Spots and How to Fix Them is a useful supplemental reference.
Before you fix anything, confirm exactly where the water starts. Under-sink leaks love to travel along pipes, drip off the lowest edge, and blame innocent parts.
Use this method:
Now do a few targeted tests:
This "dry it, then watch it" approach is the fastest way to separate supply leaks from drain leaks. If you need more general leak-response advice, our post on how to deal with a plumbing leak in your home covers the first things to do to limit damage. Another good outside reference is Sink Leaking Find the Source and Fix It DIY Guide – Total Dry Restoration.
If the leak is intermittent, place a baking tray or shallow pan under the plumbing overnight. It is not glamorous, but it works.
Once you know the exact leak point, you can decide whether to tighten, reseal, or replace.
If you are only working on the drain, you may not need to shut off the house water, but it is still smart to turn off the hot and cold shutoff valves under the sink before starting. Turn each valve clockwise until it stops.
Then:
If a shutoff valve will not turn, leaks when touched, or does not fully close, stop there and call a plumber.
Start with the least invasive fix.
Do not crank down hard on plastic fittings. Overtightening can crack them and turn a tiny drip into a bigger headache.
If a P-trap or tailpiece joint still leaks:
As a best practice, replace old washers when you take the joint apart instead of reusing them.
If the leak starts around the drain opening itself, the basket strainer seal is likely failing.
To repair it:
If the old strainer is bent, rusted, or the threads are damaged, replace the whole assembly rather than trying to save it with wishful thinking.
For more practical repair guidance, see How to Fix a Leaking Kitchen Sink | Wickes and our own roundup of simple plumbing tricks that will save you money.
Replace the P-trap if you see:
PVC traps are common and straightforward to replace. If you have an older metal trap with visible rust, replacement is usually the long-term fix.
For disposal leaks:
A disposal body leak is generally not a gasket problem. It usually means the unit is done.
After the repair:
That extra testing catches slow drips that like to wait until you think you are finished.
You do not need a truck full of gear to fix most kitchen sink drain leaks.
A basic under-sink repair kit should include:
Teflon tape can be useful on threaded pressurized plumbing connections in some cases, but it is not the cure-all for every under-sink leak. On many drain joints, the gasket does the sealing work, not the threads. Use the right material for the right connection.
If you want to build a more capable home plumbing kit, our guide to basic plumbing tips you need to know is a good next read.
The best kitchen sink leak is the one you catch before it becomes a cabinet replacement project.
A few smart habits help a lot:
Leaks waste a lot more than patience. In the U.S., household leaks waste enormous amounts of water every year, and kitchen plumbing problems are a major part of that. Mold can begin growing within 24 to 48 hours, which is one reason under-sink leaks should never be ignored.
Our plumbing maintenance checklist can help you stay ahead of hidden problems before they turn into cabinet rot, flooring damage, or musty smells.
Yes. Small drips often get worse as gaskets shrink, fittings loosen, corrosion spreads, or cabinet materials stay wet. A tiny leak can swell particleboard, cause mold in a day or two, and lead to much larger repairs if ignored. It can also waste thousands of gallons of water over time.
A good rule of thumb is every 5 to 10 years, depending on the material, age, and condition. Braided steel lines usually last longer than older rubber-style hoses, but no supply line lasts forever. Replace them sooner if you see rust, bulging, kinks, fraying, or moisture at the fittings.
Call a plumber if:
If you are in Omaha, NE or elsewhere in Nebraska, it is better to get help early than to keep feeding the drip with fresh towels and optimism.
A leaking kitchen sink drain is usually caused by a failed drain seal, worn washer, loose slip nut, cracked tailpiece, corroded P-trap, or garbage disposal connection problem. The good news is that many of these repairs are manageable if you work methodically: dry everything, test carefully, tighten only what is loose, and replace the parts that no longer seal.
The bigger lesson is simple: do not ignore a small leak. Water damage adds up fast, mold can start within 24 to 48 hours, and cabinet materials rarely forgive repeated soaking.
If you need more guidance, start with our article on how to deal with a plumbing leak in your home. And if the leak is beyond a quick DIY repair, we are here to help. At JTM Plumbing and Drain, we provide honest, affordable, and reliable plumbing service for homes and businesses in Gretna, NE and across Nebraska, including emergency help when the leak decides it will not wait.
Fill out our form or call us today!
